Molarity Molarity moles of solute per liter of

Molarity: • • Molarity ______: moles of solute per liter of solution (concentration) ________ ( M ) = moles of solute ÷ Liters of solution Molarity Grams of solute = (M) x (L) x (Molar Mass) Convert m. L to L move decimal 3 places to left moles Molarity X grams Liters M X L Molar X mass Practice Problems: 1. What is the molarity of a solution that contains 5. 5 moles of Na. Cl in 10. 5 liters of solutions? (M) = 5. 5 mol 10. 5 liters = 0. 52 M

Practice Problems 2. What is the molar concentration of an aqueous Na. Cl solution when 25. 0 grams are dissolved in water to make 500 m. L of solution? (M) = 25 grams = 0. 862 M (0. 500 L) x (58 g/mole) 3. What is the number of moles of solute in 200 m. L of a 0. 5 M solution? moles = 0. 5 M x. 2 L = 0. 1 mol 4. How many liters of a 0. 5 M solution are needed to give 2. 5 moles of solute? Liters = 2. 5 moles =. 5 M 5. 0 L

Making a Solution of a Required Concentration # of moles ÷ # of liters = Molarity

Making Dilutions • less concentrated by ____ adding Dilution: Making a solution _______ more ______. solvent Important: When diluting acids: “Add acid to water, do as you ought-er. ” A in W M 1 x. V 1=M 2 x. V 2 M 1 -- the initial concentration of the solution. V 1 -- the initial volume of the original solution that is going to be diluted with water. M 2 -- the final concentration of the solution after it’s diluted with water. V 2 -- the total volume of the final solution after it has been diluted with water.

Making Dilutions M 1 x. V 1=M 2 x. V 2 Practice Problems: 1) The science department buys HCl in large bottles that have a concentration of 12 Molar. The science teacher then dilutes the acid for labs. How would the teacher make 2. 0 liters of a 2. 5 M HCl solution from this “stock” solution? ( 12 M ) ( V 1 ) = ( 2. 5 M ) ( 2. 0 L ) V 1 = 0. 417 L Take 0. 417 L of the stock solution and add it to some water and then add enough water to make a final volume of 2. 0 liters. 2) What is the final concentration of a sugar solution if 300 m. L of water is added to 500 m. L of a 2. 5 M sugar solution? ( 2. 5 M ) (500 m. L) = ( M 2 ) ( 300 m. L ) M 2 = 4. 17 M